めっき鋼板の端面耐食性を向上させる切断技術の開発

Abstract

The Keisha-Tanmen (KT) method was developed to improve the corrosion resistance of the cut-edge surface of Zn-alloy-coated steel sheets. The dies used in the KT method have a triangular convex blade. Using the upper and lower blades, a Zn-alloy-coated steel sheet was pinched and broken off. The cut-edge surface resulting from the KT method consists of three areas: roll over, inclined plane, and fracture surface. After using the KT method, a coating could be spread effectively over the inclined plane, and the fracture surface area was decreased compared with that obtained after a conventional cutting operation, namely, shearing. The cutting behavior in the KT method was simulated by the finite element method (FEM). The reason behind the decreased fracture surface area was that the negative stress triaxiality around blade edges prevented crack generation and delayed breakage. The rate of red rust formation on the cut-edge surface after the KT method was approximately 20 % and that after shearing was approximately 60-80 % after 10-200 days of atmospheric corrosion tests. The KT method was confirmed to yield excellent corrosion resistance on the cut-edge surface of a Zn-alloy-coated steel sheet compared with that observed after a shearing operation.